Oct. 4, 2006Oct. 4, 2006

Assignment #2 MarkedAssignment #2 Marked

Lab #3 due todayLab #3 due today

Electromagnetic Radiation and HealthElectromagnetic Radiation and Health

SystemsSystems

Non-ionizing RadiationNon-ionizing Radiation

Insufficient energy to cause ionizationInsufficient energy to cause ionization

High energy non-ionizing radiation still High energy non-ionizing radiation still won’t cause ionizationwon’t cause ionization– Ionizing energy: depends on frequency not Ionizing energy: depends on frequency not

amplitudeamplitude– UV frequency: 750-800THzUV frequency: 750-800THz

Sources of Non-ionizing RadiationSources of Non-ionizing Radiation

Mostly man-made sourcesMostly man-made sourcesElectronics and electrical devicesElectronics and electrical devices– FCC/Industry Canada regulationsFCC/Industry Canada regulations

High voltage power linesHigh voltage power linesMobile phones and base stationsMobile phones and base stationsWLANs, bluetoothWLANs, bluetoothMicrowave ovensMicrowave ovensCordless phonesCordless phonesNumber is growingNumber is growing

Health Effects of Non-Ionizing Health Effects of Non-Ionizing RadiationRadiation

Thermal – increase temperature of moleculesThermal – increase temperature of molecules– Microwave ovenMicrowave oven– Smaller scale effect in any RF fieldSmaller scale effect in any RF field

Non-thermal – uncertain as to any non-thermal Non-thermal – uncertain as to any non-thermal effecteffect– Potentially: damage to cells, DNA, chromosomesPotentially: damage to cells, DNA, chromosomes

REFLEX study, Cemfec project, Interphone REFLEX study, Cemfec project, Interphone project, Perform-A project, and othersproject, Perform-A project, and others

Measuring EM ExposureMeasuring EM Exposure

Specific Absorption RateSpecific Absorption Rate– Measures absorption of EM radiation by bodyMeasures absorption of EM radiation by body– RF electronics have SAR ratings available to RF electronics have SAR ratings available to

usersusers– Less than 1.6watts/kg is max level allowedLess than 1.6watts/kg is max level allowed

Health Effects of Non-Ionizing Health Effects of Non-Ionizing RadiationRadiation

Independent Expert Group on Mobile Independent Expert Group on Mobile PhonesPhones

“ “Weight of evidence does not suggest that there are Weight of evidence does not suggest that there are adverse health effects from exposure to RF fields below adverse health effects from exposure to RF fields below guideline levels, but the published research…has guideline levels, but the published research…has limitations, and mobile phones [and WLANs] have only limitations, and mobile phones [and WLANs] have only been in widespread use for a limited time. The possibilty been in widespread use for a limited time. The possibilty therefore remains open that there could be health effects therefore remains open that there could be health effects from exposure to RF fields below guideline levels; hence from exposure to RF fields below guideline levels; hence more research is needed.”more research is needed.”

What then to do?What then to do?

What then to do?What then to do?

WHO suggests: WHO suggests: – Take precautions to minimize exposureTake precautions to minimize exposure– Limit cellphone useLimit cellphone use– Limit WLAN use (how do we do that at OC)Limit WLAN use (how do we do that at OC)– Limit wireless use by childrenLimit wireless use by children– Place high power antennas away from peoplePlace high power antennas away from people– Microcell networksMicrocell networks

EM and Health ReviewEM and Health Review

What is ionizing radiation?What is ionizing radiation?

Name 2 natural sources of ionizing Name 2 natural sources of ionizing radiation.radiation.

Name 2 man-made sources of ionizing Name 2 man-made sources of ionizing radiation.radiation.

Ionizing radiation is known to be harmful, Ionizing radiation is known to be harmful, why are there any man-made sources of why are there any man-made sources of ionizing radiation.ionizing radiation.

EM and Health Review (2)EM and Health Review (2)

When is non-ionizing radiation harmful.When is non-ionizing radiation harmful.

What is potentially the most harmful source of What is potentially the most harmful source of non-ionizing radiation that you might encounter?non-ionizing radiation that you might encounter?

Is there reason to be worried about the levels of Is there reason to be worried about the levels of non-ionizing radiation we are exposed to today? non-ionizing radiation we are exposed to today? What about in the future?What about in the future?

Which would you rather be subjected to, 60 Which would you rather be subjected to, 60 watts of 2.4 watts of 2.4 yoctohertzyoctohertz EM waves, or 60 watts EM waves, or 60 watts of 2.4 of 2.4 yottahertzyottahertz EM waves? EM waves?

SystemsSystems

SystemsSystems

Generic Communications Block Generic Communications Block DiagramDiagram

This diagram generalizes previous oneThis diagram generalizes previous one– Can be used to model entire thing or just a part of itCan be used to model entire thing or just a part of it

Qualitatively: System will do something to input Qualitatively: System will do something to input to give outputto give outputQuantitatively: If you know any two of the three Quantitatively: If you know any two of the three parts, you can figure out the thirdparts, you can figure out the third

System TypesSystem Types

Gain/LossGain/Loss

Filtering/BandlimitingFiltering/Bandlimiting

Adding NoiseAdding Noise

Changing signal typeChanging signal type

Modulating/DemodulatingModulating/Demodulating

Gain and LossGain and Loss

SigOutSigOutwattswatts = SysGain = SysGainabsRatioabsRatio x SigIn x SigInwattswatts

SigOutSigOutdBmdBm = SysGain = SysGaindBdB + SigIn + SigIndBmdBm

Filtering/BandlimitingFiltering/Bandlimiting

System prevents certain frequencies from System prevents certain frequencies from passing throughpassing through

Range allowed is between an upper cutoff Range allowed is between an upper cutoff and a lower cutoffand a lower cutoff– For low pass filters, the lower cutoff is 0For low pass filters, the lower cutoff is 0– For high pass filters, the upper cutoff is infinityFor high pass filters, the upper cutoff is infinity

Adding NoiseAdding Noise

No signal can be free of noiseNo signal can be free of noise

No system can be free of noiseNo system can be free of noise

NoiseNoiseSigOutSigOut(watts) = Noise(watts) = NoiseSystemSystem(watts) + (watts) +

NoiseNoiseSigInSigIn(watts)(watts)

Caveat: To do above calculation, noise Caveat: To do above calculation, noise must be in watts – you can’t add dBm must be in watts – you can’t add dBm togethertogether

Changing Signal TypeChanging Signal Type

Converts signal from one type to otherConverts signal from one type to other– Continuous ↔ discreteContinuous ↔ discrete– Analog ↔ digitalAnalog ↔ digital– Periodic ↔ aperiodicPeriodic ↔ aperiodic– Deterministic ↔ randomDeterministic ↔ random– Finite ↔ infiniteFinite ↔ infinite

Analog to Digital Converters (ADCs)Analog to Digital Converters (ADCs)

Digital to Analog Converters (DACs) Digital to Analog Converters (DACs)

Modulation/DemodulationModulation/Demodulation

Analog Modulation/DemodulationAnalog Modulation/Demodulation– AM: Vary signal amplitude to carry dataAM: Vary signal amplitude to carry data– FM: Vary signal frequency to carry dataFM: Vary signal frequency to carry data

Digital Modulation/DemodulationDigital Modulation/Demodulation– FSK: Use frequencies to encode/decode dataFSK: Use frequencies to encode/decode data– PSK: Use phase to encode/decode dataPSK: Use phase to encode/decode data– ASK: Use amplitude to encode/decode dataASK: Use amplitude to encode/decode data